1. Field of the Invention
The present invention relates generally to a method of fabricating a thin film transistor substrate and a thin film transistor substrate produced by the same, and more particularly to a method of fabricating a thin film transistor substrate that can improve the carrier mobility in a channel region.
2. Description of the Prior Art
Liquid crystal displays “LCDs,” which are currently the most widely used flat panel displays, include two substrates having electrodes formed thereon, and a liquid crystal layer interposed between the substrates. The liquid crystal display controls the amount of light transmitted through the liquid crystal layer by applying a voltage to the electrodes to rearrange liquid crystal molecules of the liquid crystal layer. The demand for large LCDs having a high resolution continues to increase.
More specifically, an LCD includes two substrates: one substrate (thin film transistor substrate) includes a plurality of pixel electrodes arranged in the form of a matrix, and the other substrate (common electrode substrate) has one common electrode covering the front surface of the common electrode substrate. In such an LCD, image display is achieved by applying a separate voltage to each pixel electrode. To this end, thin film transistors, which are three-terminal elements, are connected to the pixel electrodes, respectively, in order to control the voltage applied to each corresponding pixel electrode. In addition, a gate line for transferring a signal to control the thin film transistor, a data line for transferring a voltage applied to the pixel electrode, a source electrode connected to the data line, and a drain electrode spaced from and opposed to the source electrode are each formed on the substrate. The source electrode and the drain electrode are connected to each other by an active layer pattern and an ohmic contact layer pattern, which are located beneath the electrodes.
In driving such a thin film transistor, a gate-on signal Von is applied to the gate electrode, thereby transferring carrier from the source electrode to the drain electrode via a channel region; that is, via an active layer pattern exposed in a space in which the source and drain electrodes are spaced apart from each other. However, since a conventional active layer pattern has poor film quality, carrier mobility is low. To address such a problem, methods of increasing the width of the channel or decreasing the length of the channel have been researched, but such methods are also problematic in that an aperture ratio decreases and the size of the thin film transistor substrate increases.
Therefore, it would be desirable to be able to improve the carrier mobility in the channel region so as to increase the aperture ratio of the thin film transistor substrate, to decrease the size of the thin film transistor and to reduce the fabrication cost.